In a strapping machine of the type noted above, it is common to employ a chute system including a fixed wall and a movable chute, each in an arched configuration. The arched configurations enable the wall and the chute to surround a load being strapped, except where a strapping head is disposed below the load.
Typically, the chute has a generally U-shaped cross-section defining a bight and two generally parallel flanges with a space between the flanges to accommodate a strap being fed along the chute. The chute is movable toward and away from a closed position wherein the flanges bear against the fixed wall. The chute is biased toward the closed position.
Means may be provided, such as solenoid-actuated means, for moving a portion of the chute away from the fixed wall when it is desired to pull a strap from the space between the flanges. Commonly, the portion of the chute that is moved is near the strapping head, below the load. It is known, however, to employ a chute system comprising such a wall and such a chute without such means for moving a portion of the chute.
In a commonly used arrangement, the chute is mounted to the wall by a series of similar clips spaced along the chute, each clip being mounted movably on a post projecting from the wall and each clip being biased by a coiled spring toward the wall. Moreover, the coiled spring is disposed around the post, within a bore of such clip. Such an arrangement is used in Models SP-300/330 Automatic and Semi-Automatic Strapping Machines available commercially from Signode Packaging Systems (a unit of Illinois Tool Works Inc.) of Glenview, Ill., and is illustrated on pages 6-39, 6-40, of Section 6 (dated June 1992) of the Operation, Parts and Safety Manual for those Models.
Although such an arrangement has been regarded as generally satisfactory, it has been noted to have some shortcomings. Dust or other debris tends to accumulate in the bores, within which the coiled springs are disposed around the posts, whereby binding can result. Friction encountered within the bores as the chute moves toward and away from the wall also can contribute to binding. It can be difficult to replace the coiled springs or to install a new clip.
Alternative arrangements are exemplified in prior patents including Urban et al. U.S. Pat. No. 4,520,720 and Aoki et al. U.S. Pat. No. 4,011,808.